ipcomp
clen = sizeof(struct ipcomp);
struct ipcomp *ipc;
ipc = (struct ipcomp *)(mtod(m, uint8_t *) + skip);
struct ipcomp * ipcomp;
ipcomp = (struct ipcomp *)(mtod(mo, char *) + roff);
ipcomp->comp_nxt = mtod(m, struct ip *)->ip_p;
ipcomp->comp_nxt = mtod(m, struct ip6_hdr *)->ip6_nxt;
ipcomp->comp_flags = 0;
ipcomp->comp_cpi = htons(cpi);